public class AdvertisementBoard {
    Advertisement adver;
    public void setAdvertisement(Advertisement a) {
        adver = a;
    }
    public void show() {
        if(adver == null) {
            System.out.println("这是一个空的广告牌");
        } else {
            adver.showAdvertisement();
            System.out.println(adver.getCorpName());
        }
    }
}
